libaddressinput: updates to Callback

1) rename some types and variables
2) use scoped_ptr to transfer ownership around (instead of const refs of unclear origin, which may go stale at any moment)

TODO: the Helper classes need to be owned to make sure they don't run callbacks on stale objects

BUG=none
R=rouslan@chromium.org

Review URL: https://codereview.chromium.org/117823002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242017 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242017